Alkoxyamines containing a vinyl group in their molecules are known. Processes for producing such alkoxyamines are disclosed, for example, in the laid-open patent Tokukai-Sho 60-89452 and Angew. Chem. Int. Ed. Engl., 34, 1456-1459 (1995).
Namely, the alkoxyamine containing a vinyl group described in the laid-open patent Tokukai-Sho 60-89452 is obtainable by synthesis of alkoxyamine containing an OH group using special compound of azo system having an OH group in its molecule, followed by esterification of the alkoxyamine through reaction of its OH group with (meth)acryloyl chloride.
On the other hand, in the process described in Angew. Chem. Int. Ed. Engl., 34, 1456-1459 (1995), benzoyl peroxide is pyrolyzed in styrene solution under the existence of nitroxide compound. After the product of pyrolysis has hydrolyzed to produce alkoxyamine having an OH group in its molecule, alkoxyamine containing a vinyl group is obtained by introducing a vinyl group into the alkoxyamine having an OH group through reaction with chloromethylstyrene.
In the case of the said alkoxyamines containing a vinyl group according to the disclosed conventional processes, however, alkoxyamines with a functional group including an OH group are first synthesized and then combined with other vinyl compounds through ionic reaction such as esterification, etc., so that they are sensitive to ionic reaction at the combined point and thus show disadvantage to easily be dissociated to return to alkoxyamines without any vinyl group.
Moreover, all of the said conventional processes are very complicated and not desirable from industrial viewpoints because they need at least 2 steps reaction for obtaining alkoxyamines containing a vinyl group.
One of the purposes of this invention is, therefore, to provide new alkoxyamines containing a vinyl group whose frameworks are stable against ionic reaction and are useful at the same time as free radical generator, etc., as well as to provide a simple method for producing them.
On the other hand, processes for obtaining graft polymers by radical polymerization are known and disclosed, for example, in the laid-open patents Tokukai-Sho 60-89452, Tokukai-Hei 10-60064 and Tokukai-Hei 11-171946, Angew. Chem. Int. Ed. Engl., 34, 1456 (1995), Angew. Chem. Int. Ed. Engl., 36, 270 (1997) and Macromolecules, 31, 4396 (1998), which use high molecular radical polymerization initiators containing an alkoxyamine group in their molecules under the influences of stable free radicals.
The processes for obtaining high molecular radical polymerization initiators containing an alkoxyamine group in their molecules can roughly be classified into two types. In one type of process, compounds of high molecular weight have been synthesized in advance of introductions of an alkoxyamine group into their molecules through radical reaction or ionic reaction to obtain high molecular radical polymerization initiators (in the following called “Method I”). In case of the other type of process, monomer compounds containing both a radical-polymerizing vinyl group and an alkoxyamine group within the same molecule (in the following called “alkoxyamine containing a vinyl group”) are synthesized first, and then, the monomer compounds are copolymerized with other monomers to increase their molecular weight to form high molecular radical polymerization initiators (in the following called “Method II”).
In conventional processes, graft polymers are synthesized from high molecular radical polymerization initiators which have been obtained in one of the said two methods.
In case of the laid-open patents Tokukai-Sho 60-89452, Tokukai-Hei 10-60064 and Tokukai-Hei 11-171946 as well as Angew. Chem. Int. Ed. Engl., 36, 270 (1997), high molecular radical polymerization initiators are obtained by the said “Method I”.
According to the process described in the laid-open patent Tokukai-Sho 60-89452, a high polymer with general structure (polybutadien or poly(isobutyl methacrylate)) is synthesized first. Radicals generated in the said high polymer by abstraction of a hydrogen atom under the existence of nitroxide are then allowed to react with nitroxide existing in the system so as to produce high molecular radical polymerization initiator containing an alkoxyamine group suspending in its molecule.
According to the process described in the laid-open patent Tokukai-Hei 10-60064, radicals generated by photo radiation in high polymer molecule is allowed to react with nitroxide existing in the system so as to produce high molecular radical polymerization initiator containing an alkoxyamine group in its molecule.
In case of the process described in the laid-open patent Tokukai-Hei 11-171946, a peroxide group is introduced into high polymer by ozonization of polyethylene or by copolymerization of monomers containing a peroxide group in their molecules with other monomers. Then, radicals arising out of the said peroxide group by thermal cracking are allowed to react with monomers and nitroxide existing in the system in order to produce high molecular radical polymerization initiator containing an alkoxyamine group in its molecule.
According to Angew. Chem. Int. Ed. Engl., 36, 270 (1997), high molecular radical polymerization initiator containing an alkoxyamine group suspending in the high polymer molecule is obtained by producing high polymer containing a benzyl chloride group by copolymerization of styrene and chloromethyl styrene, followed by reaction of the benzyl chloride group with alkoxyamine having an OH group in its molecule.
On the other hand, high molecular radical polymerization initiators are obtained by the said “Method II” in case of the laid-open patent Tokukai-Sho 60-89452, Angew. Chem. Int. Ed. Engl., 34, 1456 (1995) and Macromolecules, 31, 4396 (1998).
Namely, according to the laid-open patent Tokukai-Sho 60-89452, radicals mainly of carbon arising out of azo compound with an OH group by pyrolysis are allowed to react with nitroxide to produce alkoxyamine with an OH group. Then, alkoxyamine containing a vinyl group is obtained by esterification of this OH group with (meth)acryloyl chloride and is further copolymerized with other monomers in order to produce radical polymerization initiator in the form of oligomer (compound of a relatively low molecular weight of 5,000 or less).
Angew. Chem. Int. Ed. Engl., 34, 1456 (1995) describes a process in which alkoxyamine containing a vinyl group, which has been obtained by reaction of chloromethyl styrene with alkoxyamine having an OH group in advance, is copolymerized with styrene so as to produce high molecular radical polymerization initiator having main chain of styrene.
Macromolecules, 31, 4396 (1998) describes a process in which alkoxyamine containing a non-conjugate vinyl group, which has been obtained by reaction between a compound with a non-conjugate vinyl group and alkoxyamine with an OH group, is copolymerized with propylene or 2-methylpentene by means of a metallocene catalyzer.
Alkoxyamine with an OH group mentioned in Angew. Chem. Int. Ed. Engl., 34, 1456 (1995) and Macromolecules, 31, 4396 (1998) is obtained by hydrolysis of the product of pyrolysis of benzoyl peroxide under the existence of nitroxide compound and styrene monomers.
The high molecular radical polymerization initiators obtained by the said conventional processes as well as the graft polymers synthesized by use of them have shown, however, the following problems:
The processes classified into “Method I” in which high molecular radical polymerization initiators are obtained through reactions of high polymer compounds as the starting material, such as hydrogen abstraction from high polymer according to the laid-open patent Tokukai-Sho 60-89452, photo reaction of high molecular compound according to the laid-open patent Tokukai-Hei 10-60064, cracking of a peroxide group in high polymer according to the laid-open patent Tokukai-Hei 11-171946, reaction of active site in high polymer according to Angew. Chem. Int. Ed. Engl., 36, 270 (1997), etc. have been unpractical because the high polymers used for those reactions have to satisfy specific requirements, respectively; they must have a hydrogen atom allowing selective and easy abstraction, they must be capable of generating radicals through light radiation or thermal treatment, they must have active site capable of reacting with an OH group, etc.
Besides, in the above mentioned processes, excessive quantities of nitroxide over the radicals arising on high molecular compounds must exist within the systems for the purpose of effective introduction of nitroxide into the high molecular compounds, what causes disadvantages in cost and requires additional processes for removing surplus nitroxide which have not participated in reactions from the produced high molecular radical polymerization initiators. Furthermore, these processes are unpractical also from industrial points of view since reactions are not easy because high polymers are used as starting materials, special equipment such as light radiator, etc. is needed, the use of solvents is inevitable and so on.
As for the process to obtain high molecular radical polymerization initiators, “Method II”, is superior to “Method I” at the above mentioned points, but still has been combined with the following problems:
In the process described in the laid-open patent Tokukai-Sho 60-89452, oligomeric radical polymerization initiator and further graft oligomer are obtained by use of alkoxyamine containing a vinyl group synthesized by esterification reaction. It shows, therefore, a structure of trunk and branch polymer combined with each other by ester bond. Since ester bond is naturally sensitive to ionic reaction, an alkoxyl group is easily released from oligomeric radical polymerization initiator. Even when graft polymer is once obtained, the branch polymer is eliminated easily so that it cannot exhibit its properties as graft polymer. It is expected from this structural defect that a coating by this graft polymer may be inferior in water resistance, resistance against acid rain, weatherproofness, etc.
The invention described in the laid-open patent Tokukai-Sho 60-89452 aims specially at obtaining oligomer so that it provides only graft polymer of a relatively low molecular weight, especially as to the branch polymer, and that the characteristics of branch polymer cannot sufficiently be exhibited. The graft polymer concerned has, therefore, been combined with the problem that it does not show sufficient effects when it is used as compatibilizer, emulsifying agent, separation stabilizing agent, etc. for mixtures consisting of 2 or more types of high polymers.
Similarly, the process described in Angew. Chem. Int. Ed. Engl., 34, 1456 (1995) provides graft polymer which has a benzilic hydrogen bonding to an oxygen atom, which is very active to radical reaction, at the combined point of trunk and branch polymer. Thus, this graft polymer has a latent structural defect that it deteriorates through decomposition as a result of gradual abstraction of such a benzilic hydrogen by oxygen radicals in the air, for example, and has a high potential of release of branch polymer from trunk. Furthermore, as for graft polymer obtainable by means of the high molecular radical polymerization initiator, synthesis of graft copolymer composed of 2 or more types of monomers is not described concretely besides description about reaction for obtaining branched styrene homopolymer. Branched homopolystyrene indicates no effects as compatibilizer, emulsifing agent, separation stabilizing agent, etc.
As being a compound with a non-conjugate vinyl group derived from aliphatic end olefin compound, the alkoxyamine containing a vinyl group described in Macromolecules, 31, 4396 (1998) allows only limited types of monomers to be copolymerized with each other if attempting to obtain high molecular radical polymerization initiator by means of radical copolymerization executable easily on industrial basis. In other words, it is difficult to obtain high molecular radical polymerization initiator with high polymer main chain composed of (meth)acrylic derivative monomers or monomers with a conjugate vinyl group such as styrene, etc.
In addition, all processes described in Angew. Chem. Int. Ed. Engl., 34, 1456 (1995) and Macromolecules, 31, 4396 (1998) require at least 3 steps reaction for obtaining alkoxyamine containing a vinyl group for the purpose of synthesis of high molecular radical polymerization initiator to be very disadvantageous in view of cost and not practical.
In consideration of the above mentioned state of things, it is the additional purposes of this invention to provide a simple process for obtaining high molecular radical polymerization initiators, which are useful in production of graft polymers, and have an alkoxyamine group bonding to their molecular main chain by carbon-to-carbon bond, as well as to provide the high molecular radical polymerization initiators obtained in such process. It is another purpose of this invention to provide high purity graft polymers stable against ionic reaction and radical reaction free from formation of homopolymers of monomers which essentially composing the branch polymer, by means of the said high molecular radical polymerization initiators.